Cathode Counting Tubes

Until recent years, high-speed electronic decimal counting devices were implemented by means of ring circuits assembled from ordinary electronic and ionic tubes. The complexity and relatively low reliability of operation of such devices hindered their wide use both in experimental and in applied electronic apparatus.

Therefore, the creation of special cathode counting tubes 1–6, each of which replaces an entire ring circuit, should be regarded as a substantial advance in the field of counting technology.

At present several basic systems of cathode counting tubes used in counting technology are known 3, 4, 5. Their operation is based on feedback between the target, on which a beam of electrons falls, and the elements that scan it. The most effective is feedback to the electrodes of the system for electrostatic deflection of the beam. Figure 1 shows the schematic diagram of the simplest counting device with a cathode tube. The cathode counting tube consists of an electron gun, electrodes 1 and 2 of the system deflecting the electron beam, a target 3, a continuous lamella 4, and an end lamella 5. Target 3 is connected to the free electrode 1 of the deflecting system. The second

deflecting electrode 2 is connected to the anode of the tube. In parallel with electrodes 1 and 2 a capacitance \(C\), shunted by a resistance \(R\), is connected.

The operation of this device is essentially as follows. When the electron beam strikes the target, the current in the latter’s circuit charges the capacitance \(C\), causing the beam to be deflected in the direction shown by arrow 7. The electron beam moves freely in this direction until it reaches the slit in target 3, through which it falls onto the solid lamella 4. The displacement of the beam, and with it the increase of the electron current on lamella 4, continues until the target current falls to the value of the discharge current of the \(C\) circuit. At this moment the motion of the beam ceases and it stops

Fig. 1.

Fig. 2.

at the edge of the slit in the target. Further motion of the beam in the same direction proves possible only if a voltage pulse applied to the deflecting plates of the tube throws the beam through the slit onto the next solid portion of the target, along which the electron beam again freely slides to the next slit. Here the electron beam again stops until the arrival of the next voltage pulse, which throws the beam through the next obstacle. Having begun the motion of the electron beam from the upper edge of the target, we are able to count the number of pulses arriving at the tube by the number of target slits overcome by the electron beam. As soon as the electron beam, in its motion along the target, reaches the end lamella 5, a current pulse in its circuit actuates a device that discharges the capacitance \(C\) and returns the beam back to the upper edge of the target.

The direct electrical feedback of the target to the sweep element may be replaced by a circuit with electronic tubes, of the kind usually used in high-speed counting devices. Along with the feedback of the target to the electrodes of the deflecting system, feedback of the target to the anode of the electron gun of the cathode commutator is also possible (Figs. 2 and 3). The mechanism of self-deflection of the electron beam with feedback of the target to the anode of the electron gun of the commutator is essentially as follows. The angle of deflection of the beam changes owing to a change in the velocity of the electrons deflected by a constant (Fig. 2) or alternating (Fig. 3) voltage. In both cases the electron current to the target charges the capacitance of the \(RC\) circuit, correspondingly lowering the anode voltage, and with it the angle of deflection of the electron beam.

For returning the electron beam to its initial position upon reaching the end lamella, two methods are used. The first and simplest of them consists in the direct discharge of the capacitance

FROM CURRENT LITERATURE

\(C\), shunting the deflecting plates, by means of the circuit shown in Fig. 1. The electron beam, having reached end lamella 5, gives a negative pulse into the circuit of the control electrode of the tube that locks the last one. The duration of the beam locking is determined by the discharge time of the capacitance \(C\) through the resistance \(R\) down to the voltage necessary for the electron beam, when switched on again, to return to the upper edge of the target. Simultaneously, a pulse is sent to the tube of the next counting digit.

Fig. 3.

Fig. 4.

A considerably shorter duration of beam return is provided by discharge cells of the capacitance \(C\), shunting the deflecting plates, constructed on electron tubes (for example, Fig. 4) or on thyratrons\(^{7}\). Good results are also obtained by using trigger circuits\(^{4}\) for this purpose.

In cathode counting tubes with an annular arrangement of the commutated electrodes, the electron beam, after traversing the circumference, automatically passes into the initial position.

The described tubes are close in their dimensions to ordinary receiving electron tubes. In a counting device they are arranged in a row, each successive tube, forming a higher counting digit, counting tens of pulses of the preceding digit. The luminous digits on the screens of the tubes, corresponding to the number of pulses received by them, make it possible directly to read off the total number of pulses registered by the apparatus.

Simplicity of operation, portability, reliability in service, and direct reading of the indications in counting devices with cathode counting tubes make it possible to use them widely in experimental and applied apparatus employed for rapid counting of electrical pulses. It is also possible to use cathode counting tubes in counting-solving devices of discrete counting, and also for the purposes of pulse selection in automatic telemechanical apparatus. In pulse selection the order \(N\) of the circuit being closed proves to be a function of the number \(n\) of pulses forming the control signal

\[ N = f(n). \]

The signals are formed by groups of identical pulses and differ from one another only in the number of pulses, and in some cases also in their sign.

L. G.

References Cited

1. J. L. Jonker, Philips Res. Rep. 5, No. 1, 6 (1950).
2. D. L. Hollway, Nature 165, No. 4204, 856 (1950).
3. H. Alfen and Romanus, Nature 160, No. 4070, 614 (1947).
4. J. L. Jonker, A. I. Ovebek and P. H. Beurs, Philips. Res. Rep. 7, No. 2, 81 (1952).
5. D. L. Hollway, Electronics 25, No. 5, 152 (1952).
6. G. A. Morton, H. Heights and L. E. Flory, Radio and Electronics 20, No. 6, 119 (1946).
7. L. A. Goncharskii, Author’s Certificate No. 48687 of 13/VII 1935, published in Bulletin of Inventions No. 7 for 1936.